Help with Cambridge Audio CD-500SE

Hi all! I have a very weird issue with my CA CD player. It started a while ago and was intermittent here and there but now its really bad.

I searched for hours on line and service manuals but kinda didn't even know where to start. So I press the power on button and the front blue screen lights up and shows the LCD numbers for a few seconds and then they go away and never come back. Leaving it plugged in over night can make it work for a few more seconds and same issue. The numbers go away but not the blue lights. At the same time, no button on the machine works. It's like it stored power in a capacitor for a few seconds and then drained completely. The drawer would open and and the laser and transport will sound like their working but then die. The problem is i can't find any information on this problem with ANY player, let alone a Cambridge. It worked fine for a while and got it super cheap and can't afford to replace it or send it away to professionally repair it either. Any hints or ideas?

I like DIY and am pretty handy with a soldiering iron but not as well with schematics. I also LOVE how it sounds so that why I'll put in some effort for this.

Only a guess at this stage, but I would start by checking the voltages around the 5V PSU voltage regulators. U1 & U2 would be good targets as these look to be feeding the digital circuits. These are 7805 regulators. Maybe one is either falling over when load is applied or something is pulling it down. The LCD and the control buttons are connected directly to the main control chip IC106. It looks like this may be losing power.

Attached Files:

The supplies to the backlight and the indication come from separate PSU regulators. I would check the outputs from these first as they are the cheapest to replace. It is possible that you have a failed rectifier, but all the PSU voltages need to be checked first. If it is the main control chip then you are in a difficult area as they are difficult to find and difficult to replace. Sorry, but I am only guessing here as I cannot measure the unit myself.
It would help if you could takes some measurements around the power supplies (or get someone else to) and then report back. This may give us a better picture as to what is happening.

Well, I've just bought one for £5, but it has a different version of the main (central) board; yours has Sony branding on it, but mine doesn't, and the front panel connectors on mine are in different positions. Differential diagnosis won't be so easy.

Display fading after the cd mechanism starts does sound like a weak PSU; power comes up, display starts, motors start, take too much current, and you get a brownout.

Well I had parts lying around and went to town replacing old stuff like original 85 degree caps with 105 degree ones so they'll last a little longer. I also went ahead and replaced the main 7808 regulator on the heat sink and on the audio board, I replaced one 7905 and 2 7805 but left the 78m05 alone because online couldn't give me a clear answer if I could replace it with a regular 7805 instead. Turned it on without the top cover and still same issue. Audio board relay clicks like it should, the blue lights light up the front panel but that's it. I have a feeling it may be the logic chip/board. Also when powered up, no sound/movement from the laser sled. The laser isn't even on. Unplugged the ribbon cable from both ends and replugged it in again and no dice. The only thing I didn't do was pop that huge Sony copper shield off and see what's underneath. It's bolted down in all four corners by huge globs of solder. It might get messy... So for the most part caps and regulators appear to be out of the equation for now. Any other suggestions?

So if I keep the unit plugged in overnight (power off), it powers up just fine for 10 seconds before dying again. Powering on and off does nothing after that, except the blue lit screen. Every power cord/wire feeding each separate circuit board is only getting a few small mV. Not good I assume. I was expecting either 12 V or 5 V. So either the transformer is bad on every single output or the KH103M discs/caps are bad on the PSU board....? Do those caps go bad? If the transformer is bad, is there any place that would sell a replacement? The transformer reads ES-48-871-1895 (also printed is ES 48 x 40).

T
So the "10np 250v Safety caps" came in the mail yesterday. Yay! I popped out the offending one and soldered the new one in. Checked everything else underneath and put it back together. Plugged in, powered on and...same junk. Blue lit screen of death. No changes.
I checked the new cap and it's getting .20 AC volts...? Is it on the earth ground wire and supposed to be that low? Before it was replaced it was in the mV. Should I just try jumping that cap instead with a piece of wire? I'm lost at this point. Maybe just buy one off of eBay.

Jumping the cap will short mains to ground (or live to neutral, depending on the position in the circuit). Loud bang ensues. Bad things happen. The fact that you asked that question suggests you do not have enough knowledge to safely fiddle with things like this, especially since you are dealing with potentially lethal mains voltages.

The capacitors on the mains input board are merely noise suppression, to stop clicks on the switch. They're on the AC, so don't expect DC voltages on them. High working voltage, small capacitance (250V, 10nF). Personally, I'd have specified a higher working voltage for a global design; 250V is barely enough for UK/European. I'd have been happier with 400V, giving a reasonable margin.

You need to check that mains voltage is getting in to the device. You will need an AC voltmeter, rated for mains voltages (e.g. 400V fsd), and suitably insulated probes.

Check the voltage between live and neutral, and follow the live path through the fuse and switch.

Once you have checked those out, check the AC output of the transformer, using the AC voltmeter on a suitable range, across the two transformer output wires.

The fact that the front panel lights up suggests that the mains input is okay, and the transformer primary winding is okay, and the secondary winding for the AC drive to the backlight is okay. Which leaves you looking at the secondary winding for the main servo board; trace the wires from transformer to main board, and measure the AC voltages where they enter the main board. It looks like they will be the red and orange wires, and the two-pin connector (bottom right of the board in the close-up picture earlier in the thread).

Wiggle the wires. Frig with the connector. Check the contacts. With the secondary winding connector removed from the main board, check the voltage from the transformer with the AC voltmeter.

Re-connect the secondary winding to the main board, and check the output of the obvious bridge rectifier (the four diodes that are probably 1N400x series devices). Most likely points to measure are at the end of the diodes furthest from the connector, and connect one lead on to a diode without the ring (0V), and the other lead to a diode with the ring (+ve). [edit] Oh balls; on closer inspection of the photo, they've laid out the PCB so that all diodes are the same orientation. In which case, find an obvious ground route (e.g. on the filter capacitors), and find the +ve output from the bridge. The obvious PCB layout for such a bridge, with diodes oriented like that is for 0V to be at the non-ring end of D125 & D126, and for +ve to be at the ringed end of D123 & D124.